The present invention relates to the fabrication of targets for sputter deposition techniques, particularly to a process for producing high density boron sputtering targets, and more particularly to a process for fabricating dense boron targets compatible with magnetron sputtering.
Free-standing foils and films of pure elemental boron are attractive for a variety of applications including x-ray optics and wear resistant hard coatings. Boron films and foils have been prepared by evaporation and in a few instances by sputtering. However, the practical deposition of boron films by the versatile magnetron sputtering process, has not been possible because of the unavailability of acceptable sputtering targets. Several approaches to fabricating sputtering targets of various materials have been developed, and are exemplified by U.S. Pat. No. 4,135,286 issued January 23, 1979 to R. J. Wright et al.; U.S. Pat. No. 4,209,375 issued Jun. 24, 1980 to W. G. Gates et al.; and U.S. Pat. No. 5,032,468 issued Jul. 16, 1991 to C. M. Dumont et al.
Dense boron is not commercially available in sufficiently large pieces for the fabrication of even the smallest sputter target. Commercially available boron sputter targets are only about 50% of theoretical density (density of 2.37gm/cc) and very fragile. Another problem that complicates the fabrication of practical boron sputter targets even from fully dense material is its poor mechanical properties. Boron is a brittle material that fractures easily when subjected to the slightest applied stress. Thus, there is a need in the art for boron sputter targets, particularly such targets which are compatible with the power densities and process parameters of a magnetron sputtering process.
The present invention satisfies this need by providing a process for fabricating practical sputter targets from a dense boron monolith prepared by a hot isostatic pressing (HIP) process. The boron sputter targets produced by this invention are suitable for operation at normal sputtering parameters by reinforcing this fragile material with a unique vacuum brazing process.